I have some confusion with scenes in Unity3d and I was not able to find any resources about them.
When should scenes be used? For example in a platformer would every level have to be a different scene? Would the main menu be a scene?
Can one overlay scenes?
How do assets work between scenes? Are they attached to each individual scene and have to be reloaded every time. Can one specify when an asset is no longer needed?
How does one send data between scenes/interface between scenes?
I understand that this is a broad topic, but I didn't want to spam with multiple questions.
When should scenes be used? For example in a platformer would every
level have to be a different scene? Would the main menu be a scene?
There are no general rules about that. In theory you may have just one scene for the whole game.
How you organize your scenes is entirely up to you and often depends on the type of game you are creating.
I think that there are at least 3 features to be considered of using scenes:
they are a logical container for all pre-instantiated objects that might be useful to divide your game into multiple levels/sections.
You can serialize cross references between GameObjects and Components inside a scene (if GO A needs a ref to GO B, and they belong to the same scene, the reference can be serialized and you no longer need to find the referenced object at runtime)
When you load (not in an additive way) another scene, the resources already loaded into memory are automatically released
Can one overlay scenes?
Yes you can using LoadAdditive. Unfortunately, once 2 scenes are both loaded into memory there is no automatic way of distinguish objects belonging to one or the other. So if you load additive a second level environment, it's up to you to keep track of the previous environment and explicitly destroy it if you need to.
How do assets work between scenes? Are they attached to each
individual scene and have to be reloaded every time. Can one specify
when an asset is no longer needed?
As defaults every GameObject of a scene will be destroyed once the new scene is loaded (unless you use an additive scene loading). A way to make a GameObject survive across scenes is to mark it using DontDestroyOnLoad.
If you need to share a particular "configuration" of a GameObject, you can store it as a prefab, and reference it across scenes (but remember that once in a scene it's a prefab instance, so the GO shares with the prefab the initial serialized and not overriden properties, but 2 instances of the same prefab are different objects).
How does one send data between scenes/interface between scenes?
Several ways, depending on what kind of persistent data you want to share.
For a particular GameObject instance let the object survive using DontDestroyOnLoad.
If you have some configuration data that doesn't need to be attached to a specific GameObject you can consider storing a ScriptableObject inside the AssetDatabase and reference it.
If you have data that must persist across different game sessions you can consider storing them into PlayerPrefs.
There are 2 other ways that I don't like, but just to cite them:
Using a static field can sometimes help you in doing that, but it has several problems from my point of view
Save and load from disk (could be useful in several situations, but often it's a platform dependent way and you can have some trouble especially on different mobile platforms)
This is a broad topic btw, I hope this answer can be a quite decent overview.
When should scenes be used? For example in a platformer would every level have to be a different scene? Would the main menu be a scene?
There is no rule as to how many scenes you need to have in your game. However, scenes allow you to logically separate out parts of your game from the rest of it. You have to have a minimum of one scene.
By main menu, if you are referring to a canvas with your UI elements, it will be IN a scene and not a scene itself. Canvas is just another GameObject, that we mostly happen to use for showing game menus. I mostly create a Canvas GameObject, put a script by the name of "UIManager" and put DontDestroyOnLoad on it, so I have access to it in all scenes. Make it Singleton and I ensure that it is not duplicated.
Can one overlay scenes?
Yes, there is no restriction as to how many scenes you can load at a time. What purpose do you plan to overlay scenes though? Maybe there is a better way than loading additively.
How do assets work between scenes? Are they attached to each individual scene and have to be reloaded every time. Can one specify when an asset is no longer needed?
Assets are what you see in your 'project' hierarchy. I think you meant "GameObject"s in the scene, and if so, think of your gameobjects as entities with components (Entity-Component System). All entities in a scene get destroyed when its parent scene is destroyed until explicitly stated not to, using DontDestroyOnLoad in some component (a monobehavior in case of unity). The destroyed ones will get garbage collected.
So how they are loaded (or reloaded) depends on your implementation, on whether you are instantiating/destroying them time an again or if you put their instantiated prefabs in a cached object and retrieving later from it.
How does one send data between scenes/interface between scenes?
Heisen covered the ones I could think of. Just to add a little bit to it, it also depends on how you want to the architect your project. So if you had an underlying data structure to e.g. hold Commands, you are free to use it in any part of your project
Most games would be organised to have scenes for every level(including the main menu) but that is entirely up to you.
You can use the data from one scene to another if you save it in a text file or binary. There are a lot of tutorials on how to do this. I find documentation helps a lot.
Assets are universal in a project.
You can not overlay scenes.
When should scenes be used? For example in a platformer would every level have to be a different scene? Would the main menu be a scene?
When to use a scene is up to you. If you are just starting I would recommend using a different scene for each section of your game.
Can one overlay scenes?
Yes, using LoadSceneMode.Additive(). (LoadAdditive() is obsolete)
How do assets work between scenes? Are they attached to each individual scene and have to be reloaded every time. Can one specify when an asset is no longer needed?
By default, assets are deleted when using SceneManager.LoadScene(). However, if you use DontDestroyOnLoad(), the object will not be destroyed when entering new scenes. If you want to only keep an object through a few scenes instead of all, use Destroy() with some boolean logic.
How does one send data between scenes/interface between scenes? I understand that this is a broad topic, but I didn't want to spam with multiple questions.
You can send data through scenes by using the aforementioned DontDestroyOnLoad(), referencing the data on different scripts, using ScriptableObjects, using JSON Serialization, using StreamWriter(), using PlayerPrefs (Don't use for important information), the list goes on. I would personally recommend using ScriptableObjects for their accessibility, and StreamWriter() for it's encryption capabilities.
Related
I'm trying to make this game using the approach of multiple scenes to make things more modular.
In my actual case I have an "Initialization" scene which holds some global state objects and the one to control the state machine of all the scenes in the game.
As for the other scenes, for now I divided them just in two: the base scenes (which for now contains everything besides UI) and its UI scenes (which basically have a Canvas and all the UI elements and UI-related scripts).
The confusion in my mind is simple though: as I tried to make the UI scenes as modular and independent as possible, there are a lot of points of interactions between the base scene and its UI scene.
For the sake of illustrating this question please take this problem I'm facing right now: I have camera animations that should be played as a response to user inputs to the UI (like the click of a button should trigger a specific camera animation). Thing is: that camera is not in the UI scene. The way I'm resolving this problem right now is creating a ScriptableObject which holds events for important actions triggered in the UI scene that are fired in the UI scene and subscribed in any other place. The same can occur in the opposite direction: the UI scene need to react to many actions that happens in other scenes.
Considering that the "camera animation" problem I explained above can happen with many other objects, if there is not a better way to handle that wouldn't splitting a game into multiple scenes be just too much of work just for the benefit of modularity? And by that I also asks: am I handling this problem the right way?
If you want to keep things consistent between scenes, there are a few ways to do it.
PlayerPrefs lets you keep variables consistent, I don't need to do a whole tutorial here, look it up.
DontDestroyOnLoad lets you take an object and make it consistent throughout the whole game. If you want, you can use DontDestroyOnLoad on one of your cameras and just delete the others in the other scenes if you want to keep a consistent camera.
I have four different Canvas elements in my Unity scene. This organizes them by concern, but also improves performance since I don't have to rebuild all the elements if I "dirty" one of them. I want to create prefabs of each so I can reuse them across the game, and also so there are less elements in my scene file (I have yet to figure out why Unity doesn't re-organize YAML to match the scene order and hierarchy. Currently I can see no reason and it makes source control a huge pain).
So, my question: Should I include the Canvas as the parent GameObject in the prefab, or should I make the first child the prefab (see image)? I see two perspectives:
On one hand it's nice to scan the list of elements in the root of the scene and see the blue objects and know they are automatically replicated across scenes. Plus, the more object stored in the prefab then there will be less to pollute my YAML file.
On the other, with a Canvas Scalar script on the parent, the sizes inside the prefab are going to be updated every time I change the resolution / platform and I've read it's not good always update them outside of prefab mode. The other issue is the fact that UI elements usually have a lot of external references to update text and so forth.
After a lot more research I've come to some conclusions about the answer:
As stated in this talk at Unite 2017, isolating UI element "islands" by concern AND how often they are updated will keep the UI from affecting performance. The video also states it is fine to use multiple Canvases inside other Canvases to achieve this goal.
If you add a prefab whose values are updated from outside the prefab they will appear as "overrides" to that prefab. This includes if you link to elements outside the prefab from within it and vice versa (see image). Importantly, it is not possible to apply these overrides to the prefab, and that's kind of the point. Unity accepts that these changes will happen and this is how it deals with them without breaking the prefab or the scene.
So the answer is yes, it's no problem to include the Canvas parent in the prefab, and you can even organize it inside other Canvas so they all inherit the same settings. Further, since the more code stored in prefabs decreases the extra (unorganized) identical code in the .unity YAML file (in my case from 17,000 lines to just less than 5000!) then this is the recommended way.
I'm making a level based game using SpriteKit. I would like to know the best practice for making level changes. I was originally using one Scene as my gameplay scene and when a level is completed, it removes all nodes in the scene and then adds the ones for the next level. I am using a background node that is persistent throughout the entire course of the game. I'm worried about memory because I don't think ARC will deallocate the nodes removed because the scene is persistent. Is this method ok or should I instantiate a new scene for when a level is changing?
The best practice is to separate game data and assets from game code. This way, you can make changes to stuff without having to recompile (and is handy if you are working with another person who doesn't code).
Here is what apple has to say about it at WWDC 2014:
When you transition between scenes, ARC will deallocate the prior scene, assuming you made no strong references to it. Since you're starting out it's unlikely you need to worry about this right now... it's mostly done with globals and closures, and you should be able to fix it if it becomes a problem (but likely won't).
You can use things like unowned self and weak var etc to ensure this doesn't happen when needed. Again this is a more advanced topic but it's good to be aware of them.
Really, making level changes is entirely up to you... if you want to make a state manager that swaps out stuff to one scene, you can certainly do that... or, you could make a bunch of scenes and transition to that. Again, the best practice here is separating game content from game code, not necessarily how you switch scenes.
Personally, I would used separate SKScenes-- because it's already built in with transitions, memory management--and you have the option of using the editor, and you get to give each scene it's own file if desired.
There is also GameplayKit which has a statemanager, in which case you could use one scene and have different states be the level.
here are some resources, buried in there are some nuggets pertaining to what you want.
https://developer.apple.com/library/content/documentation/GraphicsAnimation/Conceptual/SpriteKit_PG/DesigningGameswithSpriteKit/DesigningGameswithSpriteKit.html
https://developer.apple.com/videos/play/wwdc2014/608/
https://developer.apple.com/library/content/samplecode/DemoBots/Listings/DemoBots_SceneManager_swift.html
My problem is how to share same GUI in multiple scenes.
For example:
I have Inventory GUI on Farm scene and I need this GUI on other scenes like Castle, Dungeon etc.
It's good idea to make prefab of Canvas? Or design again the GUI? What about mixing "shared GUI" and individual GUI like Dialogs etc.?
Thanks for any answer.
You can certainly make a prefab of a canvas for each screen you need although if you have to destroy it and respawn it a lot it could cause a performance hit. An alternative is to create a single canvas with all the screens as children, all disabled, and enable each as necessary. This has the advantage of not doing lots of computation at once but on the downside there's some overhead for keeping it all in memory. For a small game I would recommend the latter and if you need to scale it up you can mix the two: have canvases with more than one related screen, ideally screens grouped in such a way that they are only accessible in certain situations, letting you keep as few canvases in the scene as possible.
Besides GUI itself you will need some scripts to handle each element and property separately.
Take a look at singleton codes; it shows how to create persistent object, which stays across different scenes.
http://wiki.unity3d.com/index.php/Singleton
It's good practice to script GUI which needs to be visible on different levels with this design pattern.
I've been developing a board-style game in Unity3D. The main scene is the board, and has the data about each player and the current (randomly-generated) board stored within it.
I intend to add minigames into the game, for example when landing on a particular space on the board. Naturally, I would like to code the minigame in a separate scene. Is there a way I can do this without losing the instance of the current scene, so that the current scene's state is maintained?
Thanks in advance :)
Short answer: no, but there may be another way to do what you want.
A basic call to Application.LoadLevel call will destroy the current scene before loading the next one. This isn't what you want.
If your minigame is relatively simple, you could use Instantiate to bring in a prefab and spawn it far away from the rest of your scene. You can even use scripts to switch to another camera, toggle player controls and other interactions in the scene, and so on. Once the minigame is done, you can destroy or disable whatever you brought in, and re-enable whatever needs to be turned on in the main scene.
You could create a separate scene and call Application.LoadLevelAdditive to load that scene without destroying the current one. As above, you can then use scripts to manage which cameras and scene behaviors are active.
If you're careful, you don't really need two separate scenes. It may be enough to "fake" a scene switch.
Hard to give a complete answer without code, but you should look into the following things either with the unity documentation or youtube:
PlayerPrefs, this is one way of saving data, although i believe it isn't entirely secure i.e. being able to edit from a text file.
Serializable, this is apparently better than playerprefs.
DonDestroyOnLoad, can carry over information to multiple scenes.
Static variables, again not sure if this will help your particular problem.